Acoustical instrument.



L. LUMIERE;

ACOUSTIGAL INSTRUMENT.

APPLICATION FILED MAY 18,1910.

Patented Sept. 24, 1912.

W/f/zeasea W ifaaawa W LOUIS LUMIERE, or LYON, rnan'cn.

ACOUSTICAL INSTRUMENT.

Specification of Letters Patent.

Patented Sept. 24, 1912.

Application filed May 18, 1910. Serial No. 561,929.

To all whom it may concern Be it known that I, Louis LUMIERE, a citizenof the Republic of France, residing at Lyon, in the Republic of France,have invented certain new and useful Improvements in AcousticalInstruments, of which the following is a full, clear, and completedisclosure. 7

This invention relates to improvements in acoustical instruments such astelephones, microphones, Stethoscopes, talking machines, musicalinstruments, and in general any instrument used for the reception ortransmission of sounds.

The invention is described below and illustrated as applied to the soundbox of a talking machine.

The invention is particularly applicable to those acousticalinstrument-s in which there is a sound box com rising asubstantiallyunchanged form throughout its whole area.

In the sound boxes of talking machines and other acoustical instrumentsthe dislacement of the movable wall has the efect of producing at thelevel of the orifice leading to the horn variations in pressure in theair within the sound box. These variations constitute the origin of theproduction of the sounds and are accompanied by a displacement of theair contained within the sound box, a displacement which travelsalternately from the orifice to the periphery ofthe sound box, and fromthe periphery to the orifice. If the internal form of the stationarywall is not correct, the displacement of the air within the sound box issubject to variations in speed which give rise to disturbances whichabsorb work and are injurious to the purity of the sound produced.

The method of construction which forms that the surface of allcylindrical sections taken between it and the movable wall aconcentrically with the axis of the orifice are equal; that is to 'say,if the diameters of these sections are taken as D D D and the height ofthese sections are taken as H H H, the surfaces of the cylinders D H =DH D H etc. It will be understood that under these conditions theinstantaneous pressure of the air will be uniform at all pointsof thesurface of the wall 0, so that the objection referred to above will beavoided and the flow of air in the sound box produced or producing-thesounds, toward and away from the orifice will be practically unaffectedby the displacement of themovable wall.

It is to be understood that this improvement is applicable whatevermaybe the form of the movable wall 0, the interior face 6 of the fixedside a being always determined by the same conditions.

Having thus described my invention, what I claim and desire to protectby Letters Patent of the United States, is

1. A sound box for acoustical instruthe surfaces of successive sectionstaken concentrically with the delivery orifice of the sound box betweenthe inner faces of the two walls are substantially equal. 7

2. A sound box for acoustical instruments comprising a stationary wallprovided with a delivery orifice, and a movable wall arranged oppositethe inner surface of said stationary wall, the inner surface of saidmovable wall and the inner surface of said stationary wall convergingradially outwardly toward each other, the surfaces of successivecylindrical sections taken coaxially with said delivery orifice betweenthe lIIHQII faces of said walls being substantially equa 3. Av sound boxfor acoustical instruments comprising a stationary wall provided with adelivery orifice, and a movable wall having an inner convex surfaceopposed to the inner surface of said stationary wall and opposite saidorifice, the inner surfaces of said stationary wall and said movableoeeaee coaxially with said delivery orifice between the inner faces ofsaid walls being substantially equal.

1 axis of said walls, being the quotient of a constant, divided by thedistance between the said point in the stationary wall and the axis ofsaid sound box.

In witness whereof I have hereunto set my hand this twenty-sixth day ofApriLA. D. 15

LOUIS LUMIERE.

Witnesses:

GAs'roN- JEAUNIAUX,

MARIN VAoHoN.

